This invention relates to a painting booth constructed on a conveyor line for continuous production of, for example, automobiles.
Automobile bodies with be taken as a typical example of articles to be painted in painting booths described in this specification although a painting booth accordng to the invention is of use also in mass production of various other articles such as household electric appliances.
On current automobile assembly lines, coating of automobile bodies with paint is performed usually in a tunnel-like enclosure, called a painting booth, through which passes a conveyor to carry the bodies. Such a painting booth is several times as long as the length of an automobile body and gives therein one spraying room which occupies an almost entire volume of the interior of the booth, so that several workers can move in this spraying room along the bodies carried on the conveyor to perform painting operation with hand spray guns at any section of the spraying room. A ventilation duct extends along the booth, usually on the ceiling of the spraying room, to blow a temperature and humidity controlled air into the spraying room. Due to the manner of painting operation in the spraying room, the arrangement of the ventilation duct and the capacity of the air conditioner are made such that air flows through every section of the spraying room at a nearly uniform rate, meaning that a uniform atmosphere is maintained throughout the spraying room. The air flows out of the spraying room together with paint dust through a grated floor of the booth and enters a washing zone which is defined between the floor and a water pit constructed below the booth. On the outside of the spraying room, ventilation ducts extend from the washing zone to discharge washed air into the atmosphere.
It is a recent trend to replace hand spray guns used in the above described painting booth with an automated spraying machine, or machines, which sprays a large quantity of paint within a limited region of the booth or the aforementioned spraying room. When such a spraying machine is introduced into a painting booth of the described type, the need of supplying air uniformly into a wide spraying room constitutes a disadvantage of the booth. Since the rate of air supply must be increased in compliance with an increased rate of paint spraying by the spraying machine, there occurs a considerable increase in the quantity of air per unit time to be supplied to the painting booth. Accordingly there arises the need of augmenting the capacity of the air conditioner including a blower, and as a result there occurs considerable increase in power and heat expenses for operation of the painting booth.